Dental caries and periodontitis are two most prevalent diseases of mankind. Although not life threatening, their morbidity continues to imposed a significant social and economic burden. The polymicrobial nature of these diseases makes them difficult to cure, and even more challenging for prevention using conventional means such as vaccination. Holistic or probiotic approaches could offer health benefits only with a deeper understanding of the inner workings of the dental biofilm community as well as their relationships with the host. Veillonella species are consistently found to be associated with dental caries and potentially periodontitis, and are speculated to contribute significantly to dental biofilm development and pathogenesis. However, due to the lack of a genetic manipulation system in this group of bacteria, our knowledge about their role in health and disease is limited at best. This project aims to establish a robust Veillonella genetic transformation system. In the first grant period, we have succeeded in obtaining the first true transformant in this genus using V. parvula strain PK1910. The current project continues the previous studies by improving transformation efficiency, constructing shuttle vectors, and creating a transformation recipient strain. Completion of these studies will establish a robust genetic transformation system for veillonellae, which will provide researchers the tools required to study Veillonella biology, physiology, ecology, and virulence under controlled laboratory conditions. PUBLIC HEALTH RELEVANCE: Dental caries and periodontitis are two most prevalent diseases of mankind, affecting the majority of children and adults, respectively, even in developed countries like the U.S. The polymicrobial etiology of these diseases makes them difficult to cure, and even more challenging for prevention through vaccination. Holistic or probiotic approaches based on understanding the ecology of the microorganisms in the dental plaque could provide viable options for disease prevention and management. This project aims to develop a genetic tool to study the biology, physiology, ecology and pathogenesis of a group of important bacteria (veillonellae) in the dental plaque, so that novel approaches can be developed for disease prevention.